JPS62160963A - Rear wheel steering controller for front/rear wheel steering vehicle - Google Patents

Abstract

PURPOSE:To bring the steering angle of rear wheel to zero when an abnormality is occurred in a vehicle speed sensor by bringing the determined steering angle ratio to zero if the abruptly varying condition of vehicle speed will continue for more than a predetermined time. CONSTITUTION:A steering angle ratio determining means 2 will determine a steering angle ratio between rear and front wheels in accordance with a detected vehicle speed. When an abrupt variation of vehicle speed is detected through an abrupt vehicle speed variation detecting means 3, a steering angle ratio modifying means 4 will fix the determined steering angle ratio for predetermined time. If the abrupt vehicle speed variation is released within a predetermined time, the fixed determined steering angle ratio is released, while if the abrupt vehicle speed variation will continue for more than a predetermined time, the determinative steering angle ratio is brought to zero.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to a rear wheel steering control device for a front and rear wheel steered vehicle, and in particular, a device for controlling the rear wheel steering angle of a front wheel steering vehicle. This invention relates to improvements in rear wheel steering control devices for front and rear wheel steered vehicles. [Background Art] Conventionally, rear wheel steering control devices for front and rear wheel steered vehicles have been disclosed, for example, in Japanese Patent Laid-Open No. 59-81272 and Japanese Patent Laid-Open No. 59-8127.
As disclosed in Publication No. 3, when the vehicle reaches a predetermined vehicle speed value and the vehicle is traveling at a lower speed than the same vehicle speed value, the steering angle ratio is set so that the rear wheel steering angle is in the opposite phase to the front wheel steering angle. Set it to a value of
Furthermore, a system has been proposed in which the steering angle ratio is set to a value such that the rear wheel steering angle is in phase with the front wheel steering angle when the vehicle is traveling at a higher speed than a predetermined vehicle speed value. According to this rear wheel steering control device, it is possible to reduce the turning radius of the vehicle during low-speed driving, and it is possible to improve the tight turning performance of the vehicle. Furthermore, when driving at medium to high speeds, the turning radius of the vehicle can be increased to allow the vehicle to change lanes quickly and easily. [Means for Solving the Problems] However, in the above-mentioned conventional device, if the vehicle speed detection section fails, when the front wheels are steered by operating the steering wheel while the vehicle is running at high speed, the rear wheels may be steered in the opposite phase to the front wheels. In such a case, if the rear wheels of a vehicle traveling at high speed are steered in the opposite phase to the front wheels, the turning radius of the vehicle will become smaller.
This poses a problem in that the vehicle is more likely to become entangled (spin), and the steering stability of the vehicle becomes unstable. On the other hand, in Utility Application No. 59-50195, the present applicant proposes that when the rear wheel steering angle is not properly linked to the front wheel steering operation,
A rear wheel steering restriction device is proposed that can maintain the rear wheels in a neutral state where the rear wheels are not steered. However, even with the above proposal, it does not operate in response to an abnormality in the vehicle speed sensor, and if the rear wheels are steered in the opposite phase while driving at high speed, the turning radius of the vehicle becomes small as described above. Therefore, there is a problem in that the vehicle gets caught in the vehicle. In addition, a rear wheel steering control device that makes the rear wheel steering angle zero in response to an abnormality in the vehicle speed sensor is disclosed in Japanese Patent Laid-Open No. 60-42160 and Japanese Patent Laid-open No. 60-60.
0-78870 etc. However, in the above proposal, it takes a certain amount of time to determine whether there is an abnormality in the vehicle speed sensor, and during this time, there is a risk that the rear wheels will be controlled in response to front wheel steering, and if the vehicle is traveling at high speed, This has a problem in that when the rear wheels are steered in the opposite phase, the turning radius of the vehicle becomes smaller as described above, causing the vehicle to become entangled.

[Purpose of the invention] The present invention has been made to solve the above-mentioned conventional problems, and is to prevent the occurrence of the vehicle being caught in the vehicle during abnormality determination when an abnormality such as a failure occurs in the vehicle speed detection means. An object of the present invention is to provide a rear wheel steering control device for a vehicle with front and rear wheel steering, which can ensure steering stability of the vehicle. [Means to solve the problem]

The present invention provides a rear wheel steering control device for a front and rear wheel steered vehicle that controls the ratio of the rear wheel steering angle to the front wheel steering angle in accordance with the vehicle speed, as shown in FIG. Depending on the vehicle speed detecting means 1 to be detected and the detected vehicle speed,
A steering angle ratio determination means 2 that determines the steering angle ratio of the rear wheel steering angle to the front wheel steering angle, a vehicle speed sudden change detection means 3 that detects a sudden change in the detected vehicle speed, and a detected vehicle speed by the vehicle speed sudden change detection means. When a sudden change is detected, the determined steering angle ratio is fixed for a predetermined time, and when the sudden change state is canceled within a predetermined time, the fixation of the determined steering angle ratio is released, and the sudden change state is canceled. continues for a predetermined time or more, a steering angle ratio changing means 4 that makes the determined steering angle ratio zero; an output means 5 that outputs a control signal corresponding to the determined steering angle ratio; The above object is achieved by including a rear wheel steering mechanism 30 that sets the rear wheel steering angle based on the determined steering angle ratio and steers the rear wheels.

[Operation] In the present invention, when a sudden change in vehicle speed is detected,
The determined steering angle ratio is fixed for a predetermined period of time. This makes it possible to prevent the rear wheels from being steered in the opposite phase, for example, when an abnormality is being determined due to a failure of the vehicle speed detection means and the vehicle is traveling at high speed. Therefore, it is possible to prevent the turning radius of the vehicle from becoming small during high-speed driving, and thereby to prevent the vehicle from getting caught in the vehicle. Further, when the sudden change in vehicle speed is canceled within a predetermined time, the fixed steering angle ratio is released. Therefore, it is possible to quickly return to the four-wheel steering state using the front and rear wheels. Further, when a sudden change in vehicle speed continues for a predetermined period of time or more, the determined steering angle ratio is set to zero. Therefore, when the vehicle speed sensor or the like is abnormal, the rear wheel steering angle can be set to zero and the vehicle can be steered by steering the front two wheels, and abnormal control of the rear wheels due to a malfunction of the vehicle speed sensor can be prevented. Embodiments Hereinafter, embodiments of a rear wheel steering control device for a front and rear wheel steered vehicle to which the present invention is adopted will be described in detail with reference to the drawings. FIG. 2 shows a front wheel steering mechanism 20, a rear wheel steering mechanism 30, and a rear wheel steering mechanism 20 of a vehicle to which the present invention is applied.
An electrical control device 40 for controlling 30 is shown. The front wheel steering mechanism 20 includes a rack and binion mechanism 2
1, and a pair of left and right relay rods 228122b connected to the rack portion of this mechanism 21. The rack and binion mechanism 21 is connected to a steering handle 24 via a steering shaft 23 at its binion portion, and transfers rotational movement of the steering handle 24 to relay rods 22a, 22.
It is converted into a reciprocating motion of b. Said left and right relay rod 2
2a and 22b are connected to the left and right front wheels 26a via left and right tie rods and left and right knuckle arms 25a and 25b (not shown).
, 26b, respectively, and the left and right front wheels 26a, 26b are steered by the left and right relay rods 22a, 22b. The rear wheel steering mechanism 30 includes a swing lever 32 for steering the rear wheels 31a and 31b in conjunction with the steering of the front wheels 26a and 26b, and a linear lever for shifting the movable fulcrum 32a of the swing lever 32. It includes an actuator 33 and a relay rod 34 that interlocks the left and right rear wheels 31a and 31b. The swing lever 32 has a fixed point 32b to which a front connecting rod 35 connected to the left knuckle arm 25a is pivoted;
and a fixing point 32c to which a rear connecting rod 36 is pivotally attached,
When the movable fulcrum 32a is between the fixed point 32b and the fixed point 32c, the fixed point 32c is displaced in the opposite direction to the fixed point 32b. Also, the movable fulcrum 32a is at a fixed point 3Gb with respect to the fixed point 32c.
If the fixed point 32c is on the opposite side to the fixed point 32b,
Displace it in the same direction. Furthermore, the movable fulcrum 32a is the fixed point 3
If it is on 2c, fixed = 7, one point 32c is not displaced. As described above, the steering angle ratio is set based on the position of the movable fulcrum 32a. The linear actuator 33 includes an actuator rod 33a connected to a movable fulcrum 32a, and by moving the actuator rod 33a in the lateral direction of the vehicle body, the movable fulcrum 32a is displaced in the same direction. The relay rod 34 connects the left and right rear wheels 31a and 31b to left and right tie rods (not shown) and left and right knuckle arms 3.
They are connected to each other via 7a and 37b. A rear connecting rod 36 is connected to the left knuckle arm 37a, and the swinging of the swinging lever 32 causes the rear wheels 31a, 31b to be connected to the left knuckle arm 37a.
I'm trying to steer the ship. The electric control device 40 calculates a target steering angle ratio K based on a vehicle speed sensor 41 that detects a vehicle speed V and the vehicle speed detected by the vehicle speed sensor 41, and calculates a target steering angle ratio K based on the vehicle speed detected by the vehicle speed sensor 41. In cooperation with the position sensor 45 that detects KS, the linear actuator 33 is adjusted so that the set steering angle ratio Ks of the swing lever 32 becomes equal to the target steering angle ratio K.
and a microcomputer 46 for controlling the . The vehicle speed sensor 41 is configured to pick up the rotation of the output shaft of the variable speed and generate a pick-up signal with a frequency proportional to the vehicle speed V. The pickup signal from the vehicle speed sensor 41 is converted into a rectangular wave signal by a waveform shaper 41a and supplied to the microcomputer 46. The position sensor 45 is connected to the linear actuator rod 3
3a, that is, the current position of the movable fulcrum 32a, and generates an analog signal representing the set steering angle ratio Ks. The analog signal of this position sensor 43 is
It is converted into a digital signal by the A/D converter 43a and supplied to the microcomputer 46 as the set steering angle ratio KS. The microcomputer 46 constitutes the steering angle ratio determining means 2, the vehicle speed sudden change detecting means 3, the steering angle ratio changing means 4, and the output means 5 in FIG.
A read-only memory (hereinafter referred to as ROM) 46a that stores a program corresponding to the flowchart shown in the figure and parameters for calculating the target steering angle ratio K, and a central processing unit (CPU) 46b that executes the program.
A writable memory (RAM) 46c that temporarily stores variables necessary for program execution, and each of the sensors 41.
The input/output interface (Il) inputs each of the 45 signals.
o) 46d, the ROM 46a, the CPU 46b,
A bus 716e commonly connects the RAM 46c and I10/16d. The 11046d is a digital-analog converter (D/A converter) that converts the digital signal output from the microcomputer 46 into an analog signal and drives and controls the linear actuator 33.
33b and a warning lamp 47 that indicates an abnormality in the vehicle speed sensor 41 is connected. The operation of the vehicle rear wheel steering control device configured as described above will be explained using the flowchart shown in FIG. When the ignition switch (not shown) is opened to start the vehicle, the CPU 46b executes step 100.
In step 102, various variables and flags are set to initial values of zero, and the warning lamp 47 is turned off. In this step 102, various variables and flags that are set to zero include vehicle speed V, which is a variable representing the detected vehicle speed, and current vehicle speed V, which is a variable representing the vehicle speed currently detected by the vehicle speed sensor 41.
n, the old vehicle speed Vo which is a variable representing the vehicle speed detected last time by the vehicle speed sensor 41, and the target steering angle ratio which is a variable which does not represent the steering angle 1hi to be set by the swing lever 32. A set steering angle ratio Ks, which is a variable representing the steering angle ratio currently set by the swing lever 32, and a timer start flag TFLG, where a value of zero indicates a timer reset state and a value of 1 indicates a timer start. , a value of zero indicates normality, a value of 1 indicates an abnormality such as a failure, and there is a vehicle speed sensor abnormality flag KFLG, and a timer one hour T which is a variable representing one hour of the timer. Next, the program proceeds to step 104, in which the waveform shaper 41 receives the signal from the vehicle speed sensor 41.
The vehicle speed V is calculated based on the vehicle speed signal supplied via the vehicle speed signal A, and the vehicle speed V is stored in the RAM 46C. Next, the process advances to step 106, and in this step 106, the calculated vehicle speed V obtained in the previous step 104 is changed to the current vehicle speed Vn.
and then store it in the RAM 46c. Next, the process proceeds to step 108, in which it is determined whether the absolute value of the difference between the old vehicle speed VO and the current vehicle speed Vn is greater than a predetermined value Vs. In this step 108, if the determination is negative, that is, the absolute value of the difference between the old vehicle speed 0 and the current vehicle speed Vn is the predetermined value Vs.
If it is determined that there is no sudden change in vehicle speed, the process proceeds to step 110. In step 110, the current vehicle speed Vn is
The target steering angle ratio K is calculated based on the parameters stored in the ROM 46a and according to the steering angle ratio characteristics shown in FIG. 4, and is stored in the RAM 46c. As a result, as shown in FIG. 4, the target steering angle ratio has the vehicle speed V
As the value increases, the absolute value is set to a value that continuously changes from a thick negative value to a large positive value, and is set to zero when the vehicle speed V is equal to a predetermined value Vo. Set. Note that a negative steering angle ratio means that the rear wheels are steered in the opposite phase to the front wheels, and a positive steering angle ratio means that the rear wheels are steered in the same phase as the front wheels. A ratio of zero means that the rear wheels are not steered. After calculating the target steering angle ratio in step 108, the program proceeds to step 112.
At , the CPU 46b reads the set steering angle ratio KS supplied from the position sensor 45 via the A/D converter 45a. Next, the process proceeds to step 114, and in step 114, the CPU 46b determines whether or not the set steering angle ratio KS is equal to the target steering angle ratio K. If it is determined in step 114 that the set steering angle ratio KS is not equal to the target steering angle ratio K, the program proceeds to step 116; Steering angle ratio KS set to angle ratio
A digital signal representing the difference between the two is output to the D/A converter 33b. This D/A converter 33b converts this digital signal into an analog signal and outputs a drive control signal of a magnitude corresponding to the above-mentioned difference to the linear actuator 33. The linear actuator 33 is an actuator rod 3
3a, the movable fulcrum 32a is displaced in the direction in which the swing lever 32 sets the target steering angle ratio K. The program then returns to step 112 where the CPU 46
b is the set steering angle ratio until 3 becomes equal to the target steering angle ratio K.
The cyclic processing of steps 112-116 continues. When the set steering angle ratio Ks becomes equal to the target steering angle ratio K through the circulation processing of steps 112 to 116, the CPU 46b
is determined to be correct in step 114, and the program proceeds to step 118. In this step 118, CP
U46b outputs a digital signal representing the difference between the target steering angle ratio and the set steering angle ratio KS, that is, zero, to the D/A converter 33b. As a result, the D/A converter 33b stops outputting the drive control signal to the linear actuator 33, and the displacement of the movable fulcrum 32a by the linear actuator 33 is stopped. After processing step 118, the program returns to step 1.
20, and in this step 120, it is determined whether the vehicle speed sensor abnormality flag 5FLG is O or not. If it is determined to be positive in this step 120, that is, if it is determined that the vehicle speed sensor 41 is normal, step 1
Proceed to step 22 and store the current vehicle speed Vn as the old vehicle speed VO in RAM46.
Thereafter, the program returns to step 104, and the CPU 46b continues the cyclic processing of steps 104 to 120, and the steering angle ratio K is set based on the steering angle ratio characteristic as shown in FIG. In this state, the steering wheel 24 is turned to the left (
When the left and right front wheels 26a, 26b are steered to the left (or to the right) in response to the rotation (or to the right), this steering force is
Left knuckle arm 25a1 front connecting rod 35, swing lever 32, rear connecting rod 36, left knuckle arm 37
It is transmitted to the a1 relay port rad 34 and the right knuckle arm 37b. As a result, the left and right rear wheels 31a131bG,
is steered according to the steering angle ratio set by the swing lever 32. At this time, if the vehicle speed V is smaller than the predetermined value Vo, the steering angle ratio is set to a negative value whose absolute value decreases as the vehicle speed V increases, so that the left and right rear wheels 31a and 31b are rotated to the right (or to the left). In other words, the left and right front wheels 26a and 26b are steered in opposite phases, and the steering angle becomes smaller as the vehicle speed V increases. Furthermore, if the vehicle speed ■ is equal to the predetermined value VO, the steering angle ratio is set to zero, so the left and right rear wheels 31a and 31b are not steered. Furthermore, if the vehicle speed V is greater than the predetermined value Vo, the steering angle ratio is set to a positive value whose absolute value increases as the vehicle speed V increases, so the left and right rear wheels 31a, 3'lb are steered toward the left (or In other words, the left and right front wheels 26a and 126b are steered in the same phase, and the steering angle increases as the vehicle speed (2) increases. On the other hand, if the determination in step 108 is positive, that is, if the absolute value of the difference between the old vehicle speed ■0 and the current vehicle speed Vn is greater than the predetermined value VS, it is determined that the vehicle speed has changed rapidly. , proceed to step 124, and this step 124
It is determined whether the timer start flag KFLG is 1 or not. If the determination in step 124 is negative, that is, if it is determined that the timer has not started,
Proceeding to step 126, the timer start flag TFL
G is set to 1. Next, proceed to step 128 and start a timer. Next, the process proceeds to step 130, in which it is determined whether the timer one hour T is smaller than a predetermined value TO. If it is determined to be positive in this step 130, that is, if it is determined that the timer one hour value is smaller than the predetermined value TO, the process returns to step 104. Moreover, if it is determined that the above-mentioned step 130 is negative,
That is, when it is determined that the timer one hour T is greater than or equal to the predetermined value 10, the process proceeds to step 132, where the vehicle speed sensor abnormality flag 5FLG is set to 1, and R
Stored on AM 46c. Next, the program proceeds to step 134, and in step 126, the target steering angle ratio K is set to zero and this steering angle ratio K is stored in the RAM 460. After processing this step 134, the program returns to step 1.
Returning to step 12, the processes from step 112 onwards are performed, and the steering angle ratio is set to zero. After setting the steering angle ratio to zero, the program proceeds to step 120, and the vehicle speed sensor abnormality flag 5FLG is set to O.
It is determined whether or not. If the determination in step 120 is negative, that is, if the vehicle speed sensor is determined to be abnormal, the program proceeds to step 136, and in step 136, a warning lamp 47 is turned on to notify that the vehicle speed sensor 41 is malfunctioning. let The program then proceeds to step 138 and
Rear wheel steering control is stopped. As can be understood from the above explanation of the operation, according to this embodiment, when the vehicle speed sensor 41 is normal, the steering angle ratio is determined based on the steering angle ratio characteristics shown in FIG. , changes continuously from negative to positive as vehicle speed V increases, and the turning radius of the vehicle increases as vehicle speed V increases. Therefore, the slip angle of the vehicle, which increases as the vehicle speed V increases and increases as the turning radius of the vehicle decreases, does not exceed a certain value, and as a result, the steering stability of the vehicle is maintained well. The vehicle's small turning performance at low speeds is fully demonstrated. On the other hand, if an abnormality occurs in the vehicle speed sensor 41, the steering angle ratio is set to the opposite phase when driving at high speed, and if the steering wheel is operated in this state, the vehicle is likely to get caught in the vehicle.
By always setting the steering angle ratio K to zero when the vehicle speed sensor 41 is abnormal, it is possible to ensure the steering stability of the vehicle when traveling at high speed. Furthermore, when detecting an abnormality in the vehicle speed sensor 41, if the absolute value of the difference between the old vehicle speed VO and the current vehicle speed Vn is greater than or equal to the predetermined value Vs, the determined steering angle ratio is determined even before the abnormality detection determination of the vehicle speed sensor 41 is made. By fixing for a predetermined period of time, it is possible to prevent the vehicle from getting caught even when the vehicle speed sensor is first opened for abnormality determination. In the above embodiment, the rear wheel steering mechanism 30 includes a swing lever 32, a linear actuator 33 that shifts the movable fulcrum 32a of the swing lever 32, and a rear wheel steering mechanism 31 that moves the left and right rear wheels 31.
Although the present invention is not limited to this, the present invention is not limited to this.
The rear wheel steering Ia structure directly drives the left and right relay rods 34 that interlock the left and right rear wheels 31a and 31b, instead of the swing lever 32 whose movable fulcrum 32a is displaced by the linear actuator 33! F71″Ijru linear actuator (
(not shown) may be provided.

【Effect of the invention】

As explained above, according to the present invention, it is possible to prevent the vehicle from getting caught even when an abnormality such as a failure occurs in the vehicle speed detection means and even during the determination of the abnormality.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main structure of a rear wheel steering control device for a front and rear wheel steered vehicle according to the present invention, and FIG. 2 is an embodiment of the rear wheel steering control device for a front and rear wheel steered vehicle according to the present invention. 1 shows a front wheel steering mechanism, a rear wheel steering mechanism, and an electric control device,
FIG. 3 is a plan view including a partial block diagram, and FIG. 3 is a flowchart showing the operation of the microcomputer in the same embodiment.
The figure is a diagram showing an example of the steering angle ratio with respect to the vehicle speed in the same embodiment. 20... Front wheel steering mechanism, 21... Rack and binion mechanism, 22a, 2
2b, 34-+) L/- [1, 24... Steering handle, 26a, 26b-... Front wheel, 30... Rear wheel steering mechanism, 31 a, 3 lb... Rear wheel, 32 ... Swinging lever, 33... Linear actuator, 40... Electric control device, 41... Vehicle speed sensor, 45... Position sensor, 46... Microcomputer.

Claims (1)

[Claims] (1) A rear wheel steering control device for a front and rear wheel steered vehicle that controls a steering angle ratio of a rear wheel steering angle to a front wheel steering angle in accordance with the vehicle speed, comprising: a vehicle speed detecting means for detecting vehicle speed; a steering angle ratio determination means for determining a steering angle ratio of a rear wheel steering angle to a front wheel steering angle; a vehicle speed sudden change detection means for detecting a sudden change in the detected vehicle speed; and a vehicle speed sudden change detection means for detecting a sudden change in the detected vehicle speed. When a sudden change in vehicle speed is detected, the determined steering angle ratio is fixed for a predetermined period of time, and when the sudden change state is canceled within a predetermined time, the fixed steering angle ratio is released, and the determined steering angle ratio is fixed for a predetermined period. When the condition continues for a predetermined period of time or more, a steering angle ratio changing means that makes the determined steering angle ratio zero; an output means that outputs a control signal corresponding to the determined steering angle ratio; and a steering angle ratio changing means that outputs a control signal corresponding to the determined steering angle ratio; A rear wheel steering control device for a front and rear wheel steered vehicle, comprising: a rear wheel steering mechanism that steers rear wheels by setting a wheel steering angle based on the determined steering angle ratio.